Circulation heaters are used in industrial processes to heat circulating fluid or gas with accurate temperature control for various processes such as heating fluids, gases and liquids, for solvent heating, analytical instrumentation, steam generation, paint heating, food and beverage heating and other industrial applications. In one known circulation heater, electric resistance heating elements are cast within an aluminum heater body wherein circulating heater tube is cast directly within this heater body. The aluminum casting transfers heat from the heating elements to the heater tube, as well as to the fluid circulating through such tubing. However, in certain sensitive applications, the metallic tubing particles can leach out of the metal tube which might cause process contamination and yield loss in the circulating fluid.
The invention relates to an improved circulation heater which avoids leaching and contamination of the process fluid being heated. More particularly, the invention relates to a circulation heater which uses a cast aluminum body, having resistance heating elements therein and also having spirally wound Teflon tubing wrapped about the heater body. The heater body is formed of cast aluminum or other suitable material and is machined to form at least one spiral channel for receiving the heater tube therein. The heater tube is preferably formed of Teflon, although other suitable non-metal, flexible tubing materials can be used. Such tubing is flexible and preferably is resiliently compressible to a certain degree and also is bendable so as to allow insertion of the tubing into the pre-cut heater channel. The tubing for the heater is pressed into the tubing channel as the heater tube is progressively wound spirally about the heater body.
The channel is formed with an undercut profile wherein the channel cross section is undercut at a narrower mouth of the channel which allows the heater tube to be compressed and then snapped into the channel. The profile of this channel insures direct contact between the tubing and the channel wall over greater than 180 degrees or more than one half of the tube circumference to increase the area of surface contact between the heater tube and channel surface. This encourages and improves heat transfer between the aluminum and the Teflon tubing since there is surface to surface contact over half of the tubing surface.
This improved circulation heater provides advantages over known circulation heaters having metal cast within the body of the heater.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.